<!DOCTYPE html>
<html lang = "en">
  <head>
    <meta charset = "utf-8">
    <title>第一次作业</title>
    <style>

    </style>
  </head>
  <body>
  <input type = "text" value = "hello world" id = "inputString"/>
  <input type = "button" value = "变为红色"/>
  <input type = "button" value = "复原"/>
  </body>
</html>
